LED lighting system

Abstract

The invention relates to a LED lighting system comprising a power supply circuit and at least one LED module. The power supply circuit comprises input terminals (K 1 , K 2 ) for connection to a supply voltage source and output terminals (K 3, K 4 ),and a driver circuit (I, II) coupled between the input terminals and the output terminals for generating a LED current out of a supply voltage supplied by the supply voltage source, and comprising a driver control circuit (II) with an input terminal (K 7 ) for receiving a current control signal and for generating a LED current in dependency of the current control signal. The at least one LED module comprises input terminals (K 5 , K 6 ) for coupling to the output terminals of the power supply circuit, a LED load (LS) coupled between the input terminals, and a module control circuit for generating a current control signal as a square wave shaped signal comprising a first part having a first amplitude during a first time lapse representing a desired magnitude of the LED current, said module control circuit comprising an AC coupling of the current control signal to the input terminal of the driver control circuit.

The invention claimed is: 
     
       1. A light emitting diode (LED) lighting system, comprising:
 a power supply circuit comprising:
 power input terminals, for connection to a power supply source, 
 output terminals, and 
 a driver circuit coupled between the power input terminals and the output terminals for generating a LED current, and the driver circuit comprising a driver control circuit with a current control input terminal, 
 at least one LED module, each of the at least one LED module comprising: 
 LED module input terminals connected to the output terminals of the power supply circuit, 
 an LED load coupled between the LED module input terminals, 
 a voltage supply circuit having input terminals connected between the LED module input terminals, and having an output terminal; and 
 a module control circuit having an input terminal connected to the output terminal of the voltage supply circuit, the module control circuit being configured to generate a current control signal, wherein the current control signal includes a first part having a first amplitude during a first time interval, a duration of the first time interval representing a desired magnitude of the LED current, said module control circuit including a series capacitor for capacitively coupling the current control signal to the current control input terminal of the driver control circuit, 
 wherein the current control signal of the at least one LED module is coupled to the control input terminal of the driver control circuit, and wherein the driver control circuit is configured to generate the LED current having a magnitude which is dependent on the duration of the first time interval of the current control signal. 
 
 
     
     
       2. The LED lighting system of  claim 1 , wherein the current control signal is temperature dependent. 
     
     
       3. The LED lighting system of  claim 2 , wherein the at least one LED module includes a coupling terminal connected to the current control input terminal of the driver control circuit for coupling the current control signal to the current control input terminal of the driver control circuit, and wherein the module control circuit comprises a temperature dependent impedance in series with the coupling terminal and wherein the driver control circuit comprises circuitry for adjusting the LED current in dependency of an amplitude of the current control signals received at the current control input terminal of the driver control circuit. 
     
     
       4. The LED lighting system of  claim 2 , wherein the current control signal further includes a second part that has a second amplitude during a second time interval, wherein a duration of the second time interval represents temperatures of LEDs in the at least one LED module. 
     
     
       5. The LED lighting system of  claim 4 , wherein the current control signal is a periodical signal, wherein each period includes the first part of the current control signal and the second part of the current control signal. 
     
     
       6. The LED lighting system of  claim 4 
 wherein the module control circuit comprises a first resistor with a resistance representing the desired magnitude of the LED current, and wherein the module control circuit comprises a timer circuit coupled to the first resistors for generating the first part of the current control signal, wherein the duration of the first time interval is a function of the resistance of the first resistor, and 
 wherein the module control circuit comprises a second resistor with a temperature dependent resistance, wherein the second resistor is coupled to the timer circuit and the timer circuit is configured to generate the second part of the current control signal, wherein the duration of the second time interval is a function of the resistance of the second resistor. 
 
     
     
       7. The LED lighting system of  claim 5 , comprising at least two LED modules, wherein the driver control circuit is equipped with circuitry for deriving the periodical current control signals generated by each of the LED modules, from a combined signal formed by superimposed AC coupled periodical current control signals generated by the LED modules. 
     
     
       8. The LED lighting system of  claim 7 , wherein the driver control circuit comprises circuitry for determining a total LED current supplied to the LED modules in dependency of a sum of the desired magnitudes of the LED current represented by the durations of the first time intervals of a first current control signals, in case the LED modules are arranged in parallel. 
     
     
       9. The LED lighting system of  claim 7 , wherein the driver control circuit comprises circuitry for determining a total LED current supplied to the LED modules in dependency of a smallest desired magnitude of the LED current represented by the duration of the first time interval in a first current control signal, in case the LED modules are arranged in series. 
     
     
       10. The LED lighting system of  claim 8 , wherein the driver control circuit comprises circuitry for decreasing the total LED current in case one or more of second parts of the current control signals indicate that temperature of said at least one LED module is too high. 
     
     
       11. The LED lighting system of  claim 1 , wherein the module control circuit comprises a first resistor with a resistance representing the desired magnitude of the LED current, and wherein the module control circuit comprises a timer circuit coupled to the first resistor for generating the first part of the current control signal, and wherein the duration of the first time interval is a function of the resistance of the first resistor. 
     
     
       12. The LED lighting system of  claim 1 , comprising at least two LED modules, wherein the driver control circuit is equipped with circuitry for deriving the desired magnitudes of the LED current of the LED modules from a combined signal formed by superimposed AC coupled periodical current control signals generated by the LED modules. 
     
     
       13. The LED lighting system of  claim 12 , wherein the module control circuits comprise circuitry for generating a second part immediately after the first part of the current control signal, and wherein the driver control circuit comprises circuitry for determining temperatures of LEDs in the LED modules from the combined signal. 
     
     
       14. The LED lighting system of  claim 12 , wherein the LED lighting system comprises circuitry for activating the module control circuits of the LED modules to generate second parts of the current control signals after a delay with respect to a start of first parts of the current control signals, the delay being longer than a longest possible first part of the current control signal, and wherein the driver control circuit comprises circuitry for deriving temperatures of LEDs in the LED modules from a second time intervals in a combined signal. 
     
     
       15. A method for operating at least one light emitting diode (LED) module comprising an LED load by means of a driver circuit comprised in a power supply circuit, the method comprising:
 generating a current control signal for the at least one LED module, wherein the current control signal includes a first part having a first amplitude during a first time interval, a duration of the first time interval representing a desired magnitude of the LED current of the at least one LED module, 
 capacitively coupling the current control signal to an input terminal of a driver control circuit via a series capacitor of a coupling circuit, 
 generating an LED current using the driver control circuit, a magnitude of the LED current being based at least in part on the duration of the first time interval of the current control signal, and 
 supplying the LED current to the LED load. 
 
     
     
       16. The method of  claim 15 , wherein the current control signal is temperature dependent. 
     
     
       17. The method of  claim 15 , wherein the current control signal further includes a second part that has a second amplitude during a second time interval, the duration of the second time interval representing temperature of the LEDs in the at least one LED module. 
     
     
       18. The method of  claim 15 , further comprising:
 communicating the current control signal from a coupling terminal of the at least one LED module to the input terminal of the driver control circuit via the capacitive coupling, wherein the driver control circuit includes an output terminal which is coupled to an input terminal of a circuit which supplies the LED current to the LED load; and 
 receiving at the coupling terminal of each LED module a triggering pulse from the input terminal of the driver control circuit, wherein the at least one LED module generates the current control signal in response to the triggering pulse. 
 
     
     
       19. A light emitting diode (LED) module, comprising:
 LED module input terminals configured to be coupled to output terminals of a power supply circuit and to receive an LED current; 
 an LED load coupled between the LED module input terminals and being configured to receive the LED current and to emit light having an intensity in correspondence to a magnitude of the LED current; 
 a module control circuit configured to generate a current control signal having a first part with a first amplitude during a first time interval, duration of the first time interval representing a desired magnitude of the LED current, 
 wherein the module control circuit includes a coupling circuit including a series capacitor configured to capacitively couple the current control signal out of the LED module to a current control input terminal of a driver control circuit of the power supply circuit. 
 
     
     
       20. The LED module of  claim 19 , wherein the module control circuit includes:
 a first resistor having a resistance value which represents the desired magnitude of the LED current; and 
 a timer circuit configured to generate the current control signal, wherein the timer circuit controls the duration of the first time interval dependent on the resistance value of the first resistor.